sSS 


MMnup^j 


City  of 


*X5~r^ 

YORK 


^QXK sr 


Sewerage  and  Sewage 
Disposal,  York.  . . . 


Paper  read  at 
a Meeting  . . . 


of  the  — 


Incorporated  Association 
of  Municipal  and  County 
Engineers,  . . . 


held  at 


The  Guildhall, 

on  the  . . 

14th  of  May, 


^ 1904.  % 


^4.  CJREER,  A..M.I.C.E., 

City  Engineer  and  Surveyor. 


%0MLJb7  H 


Paper  read  at  the  District  Meeting  of  the  Incorporated  Association 
of  Municipal  and  County  Engineers , held  at  York , May  14, 

1904. 

. 

( l-t  D R l\  f 

| — 1 r i vi  i i (Tv  ('l 

Br|v  li  C:t  f;( 


SEWERAGE  AND  SEWAGE  DISPOSAL,  YORK. 

By  ALFRED  CREEK,  Assoc.  M.  Inst.  C.E., 

City  Engineer  and  Surveyor. 

I The  first  meeting  of  the  Association  held  in  this  city  was  in 
February  1882,  under  the  presidency  of  Mr.  Lewis  Angell ; when 
papers  were  read  by  the  late  Mr.  George  Styan,  City  Surveyor 
of  York,  on  “ York  and  its  Public  Works,”  and  by  Mr.  Escott, 
until  recently  Borough  Engineer  of  Halifax,  on  “ Dwellings  for 
the  Labouring  Classes  in  our  Large  Towns.*’  ^ A second  meeting 
was  held  in  June  1888,  when  Mr.  Mawbey,  Borough  Surveyor, 
Leicester,  read  a paper  on  “ Municipal  Work  in  York.” 

The  principal  public  work  carried  out  by  the  Corporation, 
since  the  1888  meeting,  is  the  sewerage  of  the  city  and  the  dis- 
posal of  the  sewage,  and  it  is  this  subject  it  is  now  proposed  to 
refer  to. 

Sewage  disposal  is  the  most  interesting,  and  certainly  one  of 
the  most  absorbing  problems  that  we,  as  municipal  engineers, 
have  to  consider.  It  is  being  studied  with  care  and  attention 
by  a number  of  earnest  workers,  through  whose  labours  our 
knowledge  on  this  subject  is  fast  increasing.  It  is  this  general 
interest  that  promises  so  well  for  the  future,  and  leads  the  writer 
to  think  that  the  time  is  very  near  when  this  difficult  and  com- 
plex problem,  that  has  already  cost  this  country  many  millions 
of  money,  may  be  solved  on  scientific  principles,  and  when  the 
designing  and  working  of  a sewage  disposal  works  may  present 
none  of  those  uncertainties,  both  in  results  and  in  the  approval 

A 


95777 


2 


SEWERAGE  AND  SEWAGE  DISPOSAL,  YORK. 


of  the  Local  Government  Board,  that  now  trouble  the  souls  of 
the  great  majority  of  municipalities  and  their  officials. 

Yarious  standards  of  purification,  or  rather  of  impurity,  have 
been  sanctioned  provisionally  by  rivers  boards  and  county 
councils,  and  tacitly  acquiesced  in  by  the  Local  Government 
Board.  In  this  district  it  has  been  fixed  at  one  grain  of  oxygen 
absorbed  per  gallon,  and  one-tenth  of  a grain  of  albuminoid  am- 
monia per  gallon.  These  varying  standards  have  obviously  been 
fixed  by  the  various  rivers  boards  and  county  councils  to  suit  the 
different  conditions  that  obtain  in  their  respective  districts. 

In  the  Author’s  opinion  no  standard  can  be  a fair  and  equit- 
able one,  if  fixed  arbitrarily,  and  without  any  reference  to  local 
conditions,  and  to  the  proportion  the  volume  of  effluent  bears  to 
the  volume  of  the  stream  or  river  into  which  the  effluent  dis- 
charges. It  is  obviously  unfair  to  fix  upon  the  same  standard 
for  an  effluent  discharging  into  a river  with  a minimum  flow  of 
fifty  volumes  of  effluent,  as  for  an  effluent  which  forms  in  itself, 
the  bulk  of  the  volume  of  the  stream  into  which  it  is  discharged. 
In  the  latter  case  a non-putrescible  effluent  should  be  insisted 
upon,  but  surely  in  the  former  some  latitude  should  be  allowed ; 
if  it  is  allowable  to  run  crude  sewage  into  a tidal  river  it  should 
surely  be  allowable  to  discharge  an  effluent  purified  to  a limited 
extent  into  a river  of  a greater  volume  than  many  a tidal  river. 

What  the  results  of  the  labour  of  the  Royal  Commission  on 
sewage  disposal  may  be  it  is  difficult  to  forecast.  We  must 
possess  our  souls  in  patience  and  hope  that  it  may  be  a rational 
solution  of  the  problem,  moderate  and  reasonable  in  its  require- 
ments, and  with  a certain  amount  of  elasticity  in  its  working 
that  will  commend  it  to  the  majority  of  municipalities. 

Many  towns  have  during  the  past  twenty  years  spent  vast 
sums  of  money  on  works  for  the  chemical  precipitation  of  sewage, 
and  its  attendant  evils  of  sludge  pressing  and  disposal  of  cake ; 
they  are  now  in  the  position  of  having  to  begin  practically  over 
again  and  incur  additional  debt  before  the  loans  for  the  first  ex- 
penditure are  liquidated.  This  is  a matter  of  very  serious 
moment,  and  one  that  should  be  verv  seriously  considered  by 


SEWERAGE  AND  SEWAGE  DISPOSAL,  YORK. 


3 


the  Local  Government  Board  when  laying  down  hard  and  fast 
lines  for  municipalities  to  follow. 

The  Author  has  in  mind  a certain  place  in  Yorkshire  where 
the  sewage  purification  problem  has  been  shelved  from  time  to  time 
by  the  authority ; they  are  now  in  much  the  same  position  as  they 
were  thirty  years  ago ; they  have  incurred  little  or  no  expenditure 
on  works,  and  are  now  in  that  happy  position  of  knowing  that  their 
policy  of  letting  things  slide  has  resulted  in  the  saving  of  large 
sums  of  money ; while  those  municipalities,  who  have  honestly 
tried  to  deal  with  the  problem  regardless  of  cost,  are  in  the 
unfortunate  position  of  seeing  their  works  practically  con- 
demned, and,  looming  in  the  future,  further  large  expenditure 
on  works  that  may  turn  out  to  be  as  futile  and  unsatisfactory 
as  those  they  had  but  a few  years  before  carried  out  under 
pressure. 

It  is  this  uncertainty  that  the  Boyal  Commission  should  end. 
Works  carried  out  with  the  approval  of  the  Local  Government 
Board,  on  lines  laid  down  by  them,  should,  if  carried  out,  suffice 
at  least  for  a period  sufficient  to  enable  the  authority  to  pay  off 
the  debt  incurred  in  their  construction. 


Statistics. 


— 

Year. 

— 

Population  ...... 

1892 

67,807 

Ditto 

1902 

79,114 

Rateable  value 

1891 

237 , 835Z. 

Ditto  ....... 

1901 

394,763Z. 

Death  rate  per  1000  living 

1892 

20*9 

Average  death  rate  for  ten  years 

1892  to  1901 

188 

Death  rate  per  1000  living 

1902 

15*8 

Deaths  from  zymotic  diseases  for  ten  years 

1892  to  1901 

2-48 

Ditto  ....... 

1902 

1*25 

4 


SEWERAGE  AND  SEWAGE  DISPOSAL,  YORK. 


Sewerage  Works  and  Sewage  Disposal. 

It  is  proposed  to  give  some  particulars  as  to  the  cost  of  the 
York  sewerage  works  with  the  cost  of  pumping,  precipita- 
tion and  pressing,  and  also  the  results  of  experimental  works 
carried  out  during  the  past  five  years. 

The  sewerage  scheme  was  designed  and  carried  out  by  James 
Mansergh,  F.R.S.,  Past-President  of  the  Institution  of  Civil 
Engineers. 

Mr.  James  McKie,  M.  Inst.  C.E.,  acted  as  Resident  Engineer 
for  the  construction  of  the  work. 

The  contractors:  Sewers  and  river  crossings,  Mr.  A.  Kellett 
of  Ealing;  pumping  station  superstructure,  ditto;  pumping 
station  foundations,  Messrs.  Parker  and  Sharp  ; rising  main  and 
tanks  and  buildings,  at  disposal  works,  ditto ; pumping  ma- 
chinery, Messrs.  Boulton  and  Watt;  pressing  machinery  Messrs. 
Goddard,  Massey  and  Warner. 

The  works  were  commenced  in  1890,  and  with  the  exception 
of  the  house  connections  were  completed  in  1894.  The  actual, 
cost  of  the  scheme  was  as  under  : — 

£ 

Construction  of  main,  intercepting  and  a few  subsidiary 
sewers,  including  several  syphon  river  crossings  . 122,251 

Pumping  Station 18,830 

Pumping  machinery  ......  8,938 

Rising  main  and  precipitation  works,  including  cottages  28 , 882 
Precipitation  machinery  .*....  4,555 

Land  purchase,  easements,  compensation  for  damages 
and  engineer’s  commission 24,395 

Total  . . . £207,851 

The  system  for  which  the  works  were  designed  was  milk  of 
lime  treatment  followed  by  a solution  of  aluminoferric.  The 
sewage  is  naturally  alkaline. 

The  pumping  station,  situate  on  the  left  bank  of  the  river  at 
the  southern  boundary  of  the  city,  contains  : — 

Two  overhead  vertical  cylinder  triple  expansion  engines, 
each  working  three  single  acting  ram  pumps.  Each  engine  is 
capable  of  lifting  and  delivering  4,320,000  gallons  of  sewage 
per  day  through  the  27-inch  rising  main  to  the  tanks  at  Naburn 
about  two  miles  below  the  pumping  station. 

Two  centrifugal  pumps  4 feet  diameter,  direct  driven  by  two 


SEWERAGE  AND  SEWAGE  DISPOSAL,  YORK. 


5 


vertical  engines.  Each  pump  is  capable  of  lifting  and  dis- 
charging into  the  river  10,000  gallons  per  minute. 

There  are  three  Lancashire  boilers,  each  22  feet  long  by 
6 feet  6 inches  diameter,  fitted  with  Vicar’s  mechanical  stokers. 

Dynamo  for  lighting. 

A workshop  for  small  repairs,  screening  chamber,  etc.,  etc. 

The  total  average  quantity  lifted  per  annum  (over  seven 
years)  has  been  1,730,000,000  gallons,  viz.  1,239,000,000  gallons 
a maximum  lift  of  33  feet  increased  by  friction  to  about  47  feet, 
and  491,000,000  gallons  a lift  of  about  16  feet ; in  the  latter  case 
the  pumps  not  infrequently  discharge  against  a head  of  water 
in  the  river.  The  average  daily  flow  at  the  pumping  station 
over  this  period  is  4,739,000  gallons  ; the  average  cost  of  lifting 
the  1,730,000,000  gallons  has  been  20s.  1*30^.  per  million 
gallons.  The  details  for  1901,  when  the  figures  approximate 
most  nearly  to  the  average,  are  as  under : — 


Wages 

s. 

< 6 

d. 

5-34 

Coal  . 

. 8 

10*35 

Oil  and  waste 

. 1 

7-85 

General  repairs  . 

. 0 

11-95 

Water 

. 0 

2-21 

Rates,  taxes  and  insurance  . 

. 1 

0-44 

Sundries 

. 

, 1 

5-98 

Total  cost  per  million  gallons  * 20  8*12 


The  annual  cost  of  precipitation  and  pressing  during  the 
same  period  has  averaged  2Z.  4s.  11  d.  per  million  gallons  treated 
at  the  works.  Taking  the  year  1901-2  as  being  the  nearest  to 
the  average,  the  following  are  the  details  for  that  year : — 


Quantity  treated  . . . 1 , 324 , 000 , 000  gallons. 


Precipitation . 

Wages — 

Engineers  and  stokers 
Alum  mixing 
Cleaning  tanks  . 

Materials — 

Aluminoferric 

Sundries 


Cost  per  million  gallons. 

s.  d.  s.  d . i.  d. 

0 5*89 

1 3*90 

1 0 17  2 9*96 


15  0*71 

0 042  15  113 


Total  for  precipitation 


. 17  1109 


6 


SEWERAGE  AND  SEWAGE  DISPOSAL,  YORK. 


Pressing.  Cost  per  million  gallon*. 


Wages — 

s. 

d.  t. 

d . 

Engineers  and  stokers  . 

2 

1*54 

Lime  mixing 

1 

5*83 

Pressing  .... 

4 

8*08 

Maintenance,  cleaning  down, 
etc 

0 

11*72  9 

3*17 

Materials — 

Coal  . . . r 

4 

9*03 

Oil  and  Waste 

0 

4*18 

Lime 

6 

2*86 

Press  cloths 

1 

11*95 

Maintenance  of  plant  and 
machinery 

0 

3*66  13 

7*68 

Total  for  pressing 22  10*85 

General. 

Including  rates  and  taxes  and  maintenance  of 
buildings 5 1*27 

Total  cost  per  million  gallons  exclusive  of 
interest  and  sinking  fund  . . . 45  11*21 

From  February  to  December  1896,  the  sewage  was  chemi- 
cally treated  with  lime  and  aluminoferric,  the  quantity  used 
varying  with  the  quantity  of  sewage  delivered  at  the  works, 
and  to  some  extent  with  its  strength ; the  average  was  about 
five  grains  per  gallon  of  lime,  and  of  five  grains  per  gallon  of 
aluminoferric.  During  this  period  eleven  analyses  of  the  sewage 
and  effluent  were  made,  the  average  results  were  as  under : — 


— 

Oxygen  absorbed  three  hours 
at  80°. 

Albuminoid  Ammonia. 

Parts  per  100,000. 

Sewage 

4*92 

0*469 

Effluent 

1*58 

0*111 

On  these  figures  the  purification  works  out  at  67’ 8 per  cent, 
for  oxygen,  and  76  per  cent,  albuminoid  ammonia. 

The  strongest  sewage  analysed  in  this  period  was  by  oxygen 
absorbed  9*71,  and  the  weakest  1*74.  The  strongest  by  albu- 
minoid ammonia  1*406,  and  the  weakest  0*380. 

As  the  sewage  was  naturally  alkaline,  and  complaints  were 
made  as  to  the  action  of  lime  on  the  fish  in  the  river,  its  use  as 
a precipitant  was  discontinued  for  a certain  period,  and  the 
sewage  treated  with  aluminoferric  only,  the  average  quantity 


SEWERAGE  AND  SEWAGE  DISPOSAL,  YORK. 


7 


used  being  6 grains  per  gallon.  From  December  1896  to 
December  1897,  twelve  analyses  were  made  of  the  sewage  and 
effluent,  the  average  results  were  as  follows  : — 


— 

Oxygen  absorbed  three  hours. 

Albuminoid  Ammonia. 

Parts  per  100,000. 

Sewage 

7*95 

1-212 

Effluent 

2' 36 

0-266 

On  these  figures  the  purification  works  out  at  70  per  cent, 
oxygen  absorbed,  and  78  per  cent,  albuminoid  ammonia. 

The  strongest  sewage  analysed  during  this  period  was  by 
oxygen  absorbed  12*06,  and  the  weakest  3*51 ; the  strongest  by 
albuminoid  ammonia  1*406,  and  the  weakest  0 * 540. 

The  reason  why  the  sewage  was  so  much  stronger  in  the 
second  period  was  that,  during  the  intervening  time,  old  sewers 
in  the  city  were  being  connected  to  the  intercepting  sewers,  and 
as  these  had  been  waterlogged  from  the  time  of  their  construc- 
tion, and  at  the  time  of  connecting  up  were  lying  full  of  foul 
matter,  it  was  not  surprising  to  find  this  marked  increase  in  the 
foulness  of  the  sewage. 

An  examination  of  these  results  shows  the  fallacy  of  adopt- 
ing a percentage  of  purification  for  comparison,  here  we  have  an 
increase  of  4*3  in  the  percentage  of  purification,  while  the  result 
shows  the  effluent  to  be  33  per  cent,  worse  according  to  the  oxygen 
absorbed,  and  55  per  cent,  worse  according  to  the  albuminoid 
ammonia. 

A curious  feature  in  the  case  was  that  during  the  whole  of 
these  two  periods,  samples  of  the  river  water  were  taken  and 
analysed  at  the  same  time  as  the  sewage,  one  from  half-a-mile 
above  the  outlet  from  the  disposal  works,  and  one  from  half-a- 
mile  below. 

The  results  showed  an  average  of  0*258  oxygen  absorbed  in 
the  twenty-three  samples  above  the  outlet,  and  an  average  of 
0*270  oxygen  absorbed  below  the  works.  On  ten  occasions  the 
river  below  the  outlet  was  better  than  that  above,  and  on  the 
remaining  thirteen  occasions  worse.  The  greatest  difference  in 
impurity  was  found  in  the  river  water  above  the  outlet,  although 
on  the  average  it  was  less,  thus  demonstrating  as  clearly  as 
analyses  can  that  the  flow  of  sewage  effluent  into  this  river 


8 


SEWERAGE  AND  SEWAGE  DISPOSAL,  YORK. 


(rarely  flowing  at  a less  rate  than  150,000,000  gallons  a day) 
was  not  perceptible  half-a-mile  below  the  outlet. 

In  consequence  of  a number  of  dead  fish  being  found  in  the 
river  strong  complaints  were  made  by  the  fishery  board,  and  the 
West  Eiding  Eivers  Board ; they  attributed  the  destruction  of  fish 
to  the  effluent  from  the  works,  notwithstanding  that  the  same 
epidemic  in  fish  life  was  to  be  found  in  other  rivers  tributary  to 
the  Ouse,  where  no  chemically  treated  sewage  effluent  was  dis- 
charged ; dead  fish  have  frequently  been  noticed  in  the  river, 
especially  in  a very  dry  summer.  The  Author  presumes  there 
are  epidemics  in  fish  life  as  in  animal  and  bird  life. 

However,  the  Corporation  have  never  shown  any  desire  to 
shirk  their  responsibilities,  and  with  the  view  of  ascertaining  if 
they  could  in  any  way  improve  the  effluent,  empowered  the 
writer  to  experiment  in  bacteriological  and  other  methods  of 
sewage  purification. 

Accordingly,  a series  of  experiments  were  put  in  hand  in 
April  1899,  and  the  results  reported  fully  to  the  Corporation  in 
October  1901.  As  this  report  was  reprinted  in  the  technical 
papers  circulating  amongst  the  members,  it  is  proposed  only  to 
give  a brief  summary  of  the  results  obtained  up  to  that  date 
so  as  to  furnish  continuity  in  this  paper. 

Experiment  No.  1. 

COVERED  SEPTIC  TANK  AND  SINGLE  CONTACT. 

Tank  40,000  gallons  capacity.  Four  filters  each  40  feet  by 
20  feet  by  3 feet  deep.  Cycles  8 hours.  Medium,  clinker  | inch 
to  lj  inch. 


First  Period  of  Working,  April  24,  1899,  to  October  28,  1900. 
Average  of  7 Analyses.  Grains  per  Gallon. 


— 

Oxygen 

Absorbed. 

Albuminoid 

Ammonia. 

iCalcium 

Nitrate. 

Gallons  per 
Square  Yard 
per  24  Hours. 

Gallons  per 
Acre  per 

24  Hours. 

Sewage  . . 

2*430 

0-377 

Nil 

.. 

.. 

Effluent  . . 

0-805 

0*190 

Nil 

42-89 

207,580 

Percentage  of  1 
purification  / 

66-80 

49-60 

•• 

•• 

- 

» & 


SEWERAGE  AND  SEWAGE  DISPOSAL,  YORK. 


9 


Second  Period,  December  10,  1900,  to  August  1,  1901. 


Average  of  7 Analyses.  Grains  per  gallon. 


— 

Oxygen 

Absorbed. 

Albuminoid 

Ammonia. 

Calcium 

Nitrate. 

Gallons  per 
Square  Yard 
per  24  Hours. 

Gallons  per 
Acre  per 

24  Hours. 

Sewage 

Effluent  . 

Percentage  of  I 
purification  / 

3*007 

1*075 

64*  15 

0*501 

0*128 

74*35 

Nil 

Slight  tra- 
ces on  two 
occasions 

121*54 

588,225 

This  experiment  was  continued  until  1902,  but  no  better 
results  were  obtained,  and  considerable  trouble  arose  in  conse- 
quence of  the  sludging  up  of  the  filter  surface. 


Experiment  No.  2. 

CRUDE  SEWAGE  AND  DOUBLE  CONTACT  BEDS. 

No.  1 bed  90  feet  by  30  feet  by  2 feet  9 inches.  Medium, 
clinker  1^  inch  to  3 inch. 

No.  2 bed  90  feet  by  30  feet  by  2 feet  9 inches.  Medium, 
clinker  § inch  to  f inch. 

Cycle  8 hours  principally. 

August  1,  1899,  to  October  13,  1900. 


Average  of  9 Analyses.  Grains  per  gallon. 


■ 

Oxygen 

Absorbed. 

Albuminoid 

Ammouia. 

Calcium 

Nitrate. 

Gallons  per 
Square  Yard 
per  24  Hours. 

Gallons  per 
Acre  per 

24  Hours. 

Sewage 

2*341 

0*450 

Nil 

, , 

Effluent  . 

0*362 

0*101 

0*59 

31*57 

152,815 

Percentage  of  I 
purification  j 

80 

72 

•• 

•• 

•• 

10 


SEWERAGE  AND  SEWAGE  DISPOSAL,  YORK. 


Experiment  No.  3. 

LADDER-FILTER — CRUDE  SEWAGE  AND  MULTIPLE  CONTACT. 

Filter  10  compartments,  each  4 feet  by  3 feet  5 inches  by 
2 feet  deep. 

Medium,  clinker  | inch  to  f inch. 

The  10  chambers  were  arranged  in  steps  each  6 inches  below 
that  above,  the  sewage  passed  down  through  the  material  in  the 
first  chamber,  up  through  the  second,  and  so  on. 

June  8, 1899,  to  September  15,  1900. 


Average  of  3 Analyses . Grains  per  gallon. 


— 

Oxygen 

Absorbed. 

Albuminoid 

Ammonia. 

Calcium 

Nitrate. 

Gallons  per 
Acre  per 

24  Hours. 

Gallons  per 
Square  Yard 
per  24  Hours. 

Sewage 

2-365 

0-347 

Nil 

.. 

.. 

Effluent  . 

1-320 

0-220 

Nil 

72-47 

350,737 

Percentage  of  I 
purification  / 

44-2 

36-6 

•• 

•• 

•• 

Experiment  No.  4. 

OPEN  SEPTIC  TANK  AND  CONTINUOUS  FILTRATION. 

This  filter  (No.  1)  is  circular,  67  feet  6 inches  in  diameter, 
the  floor  of  Portland  cement  concrete  with  radial  grooves  on  the 
surface  1£  inch  deep  and  1J  inch  wide,  beginning  about  3 feet 
from  the  centre  and  terminating  at  the  outer  edge,  where  they 
are  about  6 inches  apart.  From  the  centre  to  the  circumference 
the  floor  has  a fall  of  about  6 inches.  Around  the  floor  and 
forming  part  of  the  same  construction  is  a shallow  channel  2 feet 
6 inches  wide  to  receive  the  filtrate  as  it  leaves  the  filter. 

On  the  concrete  floor,  about  6 inches  from  the  channel,  a 
9-inch  brick  wall  is  carried  up,  built  in  pigeon-hole  work  8 feet 
9 inches  in  height.  The  space  inside  this  wall  is  filled  up 
with  clinker  and  cinder  to  a depth  of  6£  feet.  It  would  have 


SEWERAGE  AND  SEWAGE  DISPOSAL,  YORK. 


11 


been  desirable  to  use  only  a clean  hard  material  not  likely  to  fall 
or  become  disintegrated  by  exposure  to  the  atmosphere,  or  con- 
tinuous saturation,  but  as  this  class  of  material  could  not  be 
obtained  at  a reasonable  figure  such  material  as  was  easily 
obtainable  had  to  be  used.  Part  of  the  clinker  was  of  fairly 
good  quality,  but  a large  proportion  of  it  was  insufficiently  burnt, 
and  easily  disintegrated  with  moisture. 

As  the  clinker  was  put  in  and  levelled,  perforated  unglazed 
pipes  4 inches  and  6 inches  diameter  were  laid  radially  at  three 
different  levels  at  intervals  of  2 feet  in  height  from  the  floor ; 
in  all  24  lengths  of  these  air  ducts  were  laid,  allowing  a free 
access  of  air  to  all  parts  of  the  filter,  to  these  in  a large  measure 
the  Author  attributes  the  successful  results  obtained.  They  have 
been  invaluable  in  facilitating  the  regular  observation  of  tempera- 
tures in  the  filter.  8-inch  cast-iron  pipes  are  laid  from  the  end 
of  the  open  septic  tank  down  to  and  under  the  floor  of  the  filter, 
then  carried  up  vertically  above  the  surface  level  of  the  filtering 
material. 

On  the  top  of  the  last  pipe  the  distributor  is  fixed,  and  as 
the  tank  effluent  enters  this,  it  is  spread  or  distributed  equally 
over  the  whole  area  of  the  filter  in  the  form  of  small  jets.  It 
trickles  down  through  the  filter,  emerging  at  the  floor  level  as  a 
clear  and  bright  liquid,  totally  devoid  of  smell  and  purified  to  a 
greater  degree  than  in  any  of  the  other  experiments. 

July  5,  1900,  to  August  19,  1901. 


Average  of  40  Analyses.  Grains  per  gallon. 


— 

Oxygen 

Absorbed. 

Albuminoid 

Ammonia, 

Calcium 

Nitrate, 

Gallons  per 
Square  Yard 
per  24  Hours. 

Gallons  per 
Acre  per 

24  Hours. 

Sewage 

3 024 

0-511 

Nil 

.. 

.. 

Effluent  . 

0-468 

0-049 

8-09 

440 

2,129,600 

Percentage  of  1 

84-5 

90-0 

purification  / 

The  worst  results  obtained  during  this  period  were  : — 

Oxygen  absorbed  ......  0 896 

Albuminoid  ammonia,  . . . . . 0 090 

Calcium  nitrate  . . . . . . . 104 

A 4 


12 


SEWERAGE  AND  SEWAGE  DISPOSAL,  YORK. 


The  best  result  obtained  was : — 

Oxygen  absorbed  . 

Albuminoid  ammonia 
Calcium  nitrate  . . 4 


0-114 
0 021 
20-51 


Experiment  No.  5. 

OPEN  SEPTIC  TANK  EFFLUENT  AND  DOUBLE  CONTACT. 

Tank  160  feet  by  40  feet  by  6 feet  6 inches  (part  of  flow  used 
for  this  experiment). 

November,  1900,  to  April  25,  1901. 

Average  of  16  Analyses,  Grains  per  gallon. 


— 

Oxygen 

Absorbed. 

Albuminoid 

Ammonia. 

Calcium 

Nitrate. 

Gallons  per 
Square  Yard 
per  24  Hours. 

Gallons  per 
Acre  per 

24  Hours. 

Sewage 

3 031 

0-551 

Nil 

.. 

.. 

Effluent  . 

0-647 

0-068 

1-97 

37  04 

179,298 

Percentage  of  1 
purification  / 

78-6 

87-6 

V 

•• 

•• 

This  disposes  of  the  results  obtained  up  to  the  end  of  August 
1901. 

It  is  not  surprising  under  the  circumstances  that  it  was 
decided  to  discontinue  experiments  Nos.  1,  2,  3 and  5,  while 
experiment  No.  4 was  continued  on  the  same  lines ; on 
March  12,  1902,  the  filter  was  stopped  to  allow  of  the  construc- 
tion of  a grit  chamber  at  the  entrance  to  the  open  septic  tank. 

Continuing  the  record  of  results  given  under  No.  4 (see  above) 
the  following  are  the  figures  up  to  the  stopping  of  the  filter  on 
March  12,  1902. 

Up  to  this  date  the  crude  sewage  had,  after  rough  screening, 
been  run  into  the  open  septic  tank  and  no  attempt  made  to  inter- 
cept grit ; it  was  therefore  decided  to  wall  off  part  of  the  tank 
10  feet  6 inches  by  39  feet  6 inches  by  7 feet  at  the  inlet  end, 
so  as  to  form  a chamber  for  the  deposition  of  grit  and  other 


SEWERAGE  AND  SEWAGE  DISPOSAL,  YORK. 


13 


Date 

of  Analyses. 

Gallons 
per  Square 
Yard  per 

24  hours. 

Sewage. 

Effluent. 

Calcium 

N itrate. 

Oxygen. 

Albuminoid. 

Ammonia. 

Oxygen 
Abso  bed. 

Albuminoid. 

Ammonia. 

1901 

Sept.  10  . 

390 

3*23 

0*65 

0*40 

0*05 

7-93 

„ 18  . 

390 

3*43 

1*20 

0*43 

0*09 

8*19 

„ 26  . 

475 

2*45 

0*41 

0*47 

003 

9*84 

Oct.  1 . 

475 

5*78 

0*32 

0*31 

004 

8*20 

» 8 . 

475 

5-49 

0*33 

0*34 

0*05 

8*20 

„ 23  . 

475 

1*82 

0*65 

0*32 

0*08 

8*61 

Not.  6 . 

475 

3-01 

0*52 

0-36 

008 

2*46 

„ 27  . 

475 

3*90 

0*45 

0*35 

0*08 

3*69 

Dec.  11  . 

475 

2*38 

0*58 

0*20 

0*06 

6*97 

27  . 

475 

2*82 

0*50 

0*28 

006 

5*33 

1902 

Jan.  8 . 

475 

.. 

.. 

0*65 

0*07 

3*85 

» 13  . 

475 

5*95 

043 

062 

005 

8*20 

Mar.  6 . 

475 

2-05 

0-42 

0*43 

0*06 

•• 

Average 

3*53 

0*54 

0*32 

0*06 

6*79 

heavy  substances.  This,  and  other  works  hereafter  referred  to, 
occupied  until  May  7, 1902,  when  the  working  of  the  continuous 
filter  was  resumed. 

Up  to  this  date  (March  7,  1902)  the  tank  and  filter  had 
passed  105,000,000  gallons  of  sewage,  equal  to  464  gallons  per 
square  yard  per  twenty-four  hours  over  the  actual  days  working, 
or  426  gallons  per  yard  per  day  over  the  whole  period.  This 
quantity  represents  over  thirty  days’  normal  flow  from  the  en- 
tire city. 

In  the  interval  between  stopping  the  filter  on  March  12,  for 
the  formation  of  a grit  chamber  and  the  restarting  on  May  7 
(fifty-six  days),  the  sewage  in  the  tank  was  drawn  off,  when  the 
sludge  was  found  to  average  a depth  of  20  inches  over  the  whole 
tank,  or  about  390  cubic  yards,  representing  1 cubic  yard  to 
about  270,000  gallons  of  sewage,  whereas  with  chemical  precipi- 
tation the  sludge  would  have  been  about  3570  cubic  yards,  or  1 
cubic  yard  to  say  30,000  gallons.  The  sludge  was  cleared  out 
and  the  grit  chamber  wall  constructed. 


14  SEWERAGE  AND  SEWAGE  DISPOSAL,  YORK. 

During  the  same  period  one-half  of  the  circular  filter  was 
opened  into,  the  material  was  found  to  be  quite  clean,  the  gela- 
tinous substance  that  under  working  conditions  surrounds  each 
piece  of  clinker  had  disappeared  leaving  a thin  covering  of  grit 
adhering  to  the  surfaces  of  the  material ; the  only  smell  observ- 
able was  that  of  newly-turned  earth.  The  opening  into  the 
material  was  continued  over  the  whole  of  the  eastern  half  of 
the  filter,  down  to  the  concrete  floor,  and  the  material  turned 
over. 

With  the  exception  of  the  bottom  9 inches,  the  whole  of  the 
material  in  that  half  of  the  filter  disturbed  was  similar  to  that 
already  described  ; the  bottom  9 inches  resting  on  the  floor  was 
found  to  be  composed  of  fine  gritty  ashes,  the  result  of  the  dis- 
integration of  the  filtering  medium ; this  was  cleared  away  and 
the  half  of  the  floor  exposed,  covered  with  old  pan  tiles  placed  on 
old  bricks  laid  radially  between  the  grooves  in  the  floor.  All 
the  old  filtering  material  with  the  exception  of  the  very  fine  was 
then  replaced  and  sufficient  new  clinker  added  to  make  up  the 
deficiency.  The  old  bricks  and  pan  tiles  left  a space  of  about 
4 inches  between  the  concrete  floor  and  the  underside  of  the  pan 
tiles,  forming  so  many  open  ducts  for  the  access  of  air  to  the 
bottom  of  the  filter,  in  addition  to  the  perforated  pipes  laid  in 
the  body  of  the  filter. 

On  May  7,  1902,  the  filter  was  restarted,  the  westerly  half 
remaining  undisturbed  as  put  in  April  and  May  1900. 

Up  to  the  20th  of  the  month  about  288  gallons  per  square 
yard  per  day  were  passed  through  the  filter ; from  the  20th  to 
the  29th,  315  gallons;  and  from  the  29th  to  June  14,  341 
gallons,  the  effluent  being  bright  and  clear.  The  suspended 
matter  from  the  east  side  had  the  appearance  of  white  ash  and 
was  sufficiently  heavy  to  lie  in  the  channel  surrounding  the  filter  ; 
the  suspended  matter  from  the  west  or  undisturbed  side  was 
more  flocculent.  That  from  the  east  side  of  the  filter  averaged 
2*26  grains  per  gallon  of  suspended  matter,  while  that  from  the 
west  side  averaged  4*62  grains,  this  was  from  July  to  November 
1902.  At  the  close  of  this  period,  the  analyses  of  the  two 
approximated  so  closely  that  further  separate  analyses  were  not 
considered  necessary. 

From  the  restarting  of  the  filter  to  November  4,  samples  for 
analysis  were  taken  from  each  side  of  the  filter,  and  the  results 
are  given  in  detail  for  the  purpose  of  comparison. 


SEWERAGE  AND  SEWAGE  DISPOSAL,  YORK. 


15 


The  quantities  passed  through  the  filter  varied  from  288 
gallons  to  515  gallons  per  square  yard  per  twenty-four  hours  as 
per  the  following  table,  together  with  the  results  in  grains  per 
gallon. 


Date. 

Gallons 
per  Square 

Sewage. 

East,  or 
Disturbed  Side. 

West,  or 

Undisturbed  Side. 

Yard  per 
24  Hours. 

Oxygen. 

Albu- 

minoid. 

Oxygen. 

Albu- 

minoid. 

Oxygen. 

Albu- 

minoid. 

1902. 
May  28. 

288 

6*22 

0-35 

0*47 

June  11. 

515 

4*48 

0-50 

0*39 

004 

0*34 

003 

July  1. 

515 

1*86 

0*63 

042 

0-06 

0*40 

0*05 

» 8. 

515 

2*17 

0*42 

0-47 

0-04 

0*32 

0*03 

Aug.  5 . 

515 

365 

0*81 

0-47 

0-04 

043 

0*06 

» 12. 

515 

6-50 

0*55 

0*41 

0*06 

0*34 

0*06 

„ 26. 

515 

2-84 

0-56 

0*49 

0-06 

0*52 

0*05 

Sept.  23. 

515 

2*54 

0*52 

0*45 

0-06 

0-53 

0-07 

Oct.  9. 

515 

7*92 

0-39 

0-33 

0*07 

0-26 

0*07 

„ 21. 

490 

4*07 

0*66 

0*51 

014 

0*44 

0*11 

Nov.  4 . 

450 

3-71 

0-03 

0*51 

0-07 

0*51 

006 

Average 

• 

468 

4-09 

054 

0-45 

0*06 

037 

0-05 

Percentage  of  purifica-j 
tion / 

•• 

•• 

89 

89 

91 

91 

Up  to  this  date  both  sewage  and  effluent  had  been  allowed 
to  settle  before  analysing.  The  reason  why  this  course  was 
adopted  was  that  Dr.  Smith,  the  medical  officer  for  the  City  and 
and  analyst  to  the  Sewerage  Committee,  considered  it  the  fairest 
course  to  adopt ; he  is  of  opinion  that  the  mineral  matter  in  the 
liquid  takes  up  a certain  portion  of  permanganate,  and  conse- 
quently shows  on  analysis  an  excessive  absorption  of  oxygen, 
not  due  to  organic  matter  in  the  sewage.  An  additional  reason 
was  that  on  enquiry  from  ten  analysts  it  was  found  that  five 
analysed  after  shaking  up  the  effluent,  so  as  to  obtain  part  of 
the  solid  impurities,  and  five  analysed  after  settlement  of  the 
solids.  To  be  on  the  right  side  therefore,  it  was  decided  from 
this  date  to  shake  up  all  samples  at  the  time  of  analysis. 

The  further  results  from  this  filter  between  November  4, 


16 


SEWERAGE  AND  SEWAGE  DISPOSAL,  YORK. 


1902,  and  the  end  of  March  1904,  show  pretty  much  the  same 
results  as  those  already  referred  to.  The  Author  does  not  wish  to 
overburden  the  paper  with  figures  ; he  therefore  gives  the  average 
of  the  (30)  analyses  made  during  this  period. 


November  18, 1902,  to  March  22,  1904. 
Average  of  30  Analyses.  Grains  per  gallon. 


— 

Oxygen 

Absorbed. 

Albuminoid 

Ammonia 

Calcium 

Nitrate. 

Gallons  per 
Square  Yard 
per  24  Hours. 

Sewage 

540 

117 

.. 

.. 

Effluent  

0-57 

Oil 

9*48 

380 

From  June  1903,  the  samples  were  tested  after  incubation 
for  five  days  at  80  degrees,  and  in  all  cases  the  effluent  was 
found  to  be  non-putreseible. 

This  filter  has,  up  to  the  end  of  March,  been  at  work  for 
three  years  and  nine  months  ; it  was  built  on  economical  lines, 
the  walls  of  common  local  bricks  and  the  filtering  medium  of  a 
very  poor  description  ; it  has  nevertheless  done  excellent  work 
during  this  period  in  having  passed  209,808,000  gallons  of 
sewage  and  along  with  the  septic  tank  effected  such  a purification 
that  on  leaving  the  filter  it  contains  only  half  the  impurity 
allowed  by  the  West  Eiding  Rivers  Board,  and  is  absolutely 
non-putrescible. 

From  May  7 to  August  1,  1902,  2 feet  6 inches  of  sediment 
had  accumulated  in  the  grit  chamber,  there  was,  at  the  latter 
date  an  entire  absence  of  scum  both  on  the  grit  chamber,  and  on 
the  open  septic  tank,  the  average  depth  of  sludge  in  the  bottom 
of  the  open  septic  tank  was  3 inches. 

The  grit  was  cleaned  out  for  the  first  time  on  September  4,  at 
this  date  a 2-inch  scum  covered  the  surface  of  both  the  grit 
chamber  and  the  open  septic  tank.  (See  Diagram  No.  2,  show- 
ing depth  of  sludge  after  one  and  two  years  respectively.) 

The  depth  of  sludge  was  4 feet  10  inches,  and  occupied 
about  2000  cubic  feet  of  the  chamber.  As  21^  million  gallons 
of  sewage  had  passed  through,  this  would  be  equal  to  1 cubic 
yard  to  290,000  gallons  of  sewage ; of  course  it  will  be  under- 
stood that  this  sludge  was  not  all  mineral  matter.  Dr.  E.  Smith, 
analyst  to  the  Sewerage  Committee,  says,  “ The  organic,  volatile 


SEWERAGE  AND  SEWAGE  DISPOSAL,  YORK.  17 

and  combustible  matters  (including  numerous  bits  of  wood  and 
woody  fibre,  hair,  stalks,  etc.)  amounted  to  45  per  cent,  of  the 
dry  residue,  leaving  55  per  cent,  non-volatile,  non-combustible, 
mineral  matter.  I made  rough  tests  for  nitrogen  and  phosphates ; 
there  was  a large  amount  of  organic  nitrogen,  the  residue  was 
also  rich  in  phosphates,  so  that  the  residue  would  make  a very 
good  manure,  although  the  large  amount  of  woody  fibre  would 
probably  prove  inconvenient  in  a manure.” 

From  observation  since  made,  the  writer  has  come  to  the  con- 
clusion that,  under  the  circumstances  that  obtain  in  this  experi- 
ment, the  chamber  should  be  cleaned  out  once  in  every  two  or 
three  weeks. 

The  very  satisfactory  results  obtained  from  the  open  septic 
tank  and  continuous  filter  induced  the  Sewerage  Committee  to 
construct  a second  continuous  filter  on  somewhat  similar  lines, 
endeavouring  in  the  new  work  to  ascertain  what  kind  of  filtering 
media  would  give  the  best  results ; accordingly  the  adjoining 
precipitation  tank  No.  5,  160  feet  by  40  feet  by  7 feet,  was  con- 
verted into  an  additional  open  septic  tank,  and  a new  filter  100 
feet  internal  diameter  constructed. 

This  work  necessitated  some  little  interruption  in  the  work 
of  No.  1 tank  and  filter,  but  with  the  exception  of  about  two 
days,  the  old  plant  was  kept  at  work  during  the  alterations. 

With  the  additional  tank,  a total  capacity  of  478,650  gallons 
is  provided  for  septicising  the  sewage. 

The  cubic  capacity  of  the  open  septic  tank  provision  is  2836 
cubic  yards. 

The  filter  contents : 

Cnbic  yards. 

No.  1 . . . . 900 

No.  2 . . . . 2182 

Total  . . 3082 

or  0 * 9 of  tank  capacity  to  1 of  filter  contents.  At  present  we 
have  an  excess  of  tank  capacity,  but  this  will  be  remedied  when 
a third  filter  is  constructed. 

The  second  tank  is  not  used  separately  as  distinct  from  No.  1. 
The  crude  sewage  flows  in  at  the  top  level  of  the  grit  chamber, 
over  a weir  wall,  into  and  through  No.  1 open  septic  tank,  over 
a second  weir,  into  and  through  No.  2 open  septic  tank,  and  from 
thence  to  the  filters.  In  no  case  does  the  sewage  flow  through 
submerged  openings. 


18 


SEWERAGE  AND  SEWAGE  DISPOSAL,  YORK. 


From  the  outlet  end  of  No.  2 tank  the  tank  effluent  flows 
into  two  channels,  one  for  each  filter,  and  in  so  doing  passes 
over  two  notch  gauges,  these  are  proportionate  to  the  area  of  the 
filters,  so  that  under  ordinary  conditions  each  filter  receives  the 
proportion  due  to  its  area.  Valves  are  provided  for  increasing  or 
reducing  the  quantity  passing  to  each  filter  when  required  for 
experimental  purposes.  The  average  depth  of  sludge  in  tanks 
at  various  dates  is  shown  on  Diagram  No.  3. 

The  new  filter  (No.  2)  is  of  somewhat  different  construction 
from  No.  1. 

The  floor  falls  from  the  outside  rim  to  the  centre,  the  object 
of  this  is  to  retain  as  far  as  possible  any  disintegrated  material 
that  may  fall  to  the  bottom,  and  the  suspended  matter  in  the 
filtrate.  This  can  be  removed  when  a sufficient  quantity  has 
accumulated,  by  means  of  pipes  communicating  with  a trench  in 
the  land  adjoining  the  filter. 

The  floor  is  formed  of  8 inches  of  concrete  with  old  railway 
rails  embedded  in  it ; on  the  floor  are  built  4^-inch  pigeon-hole 
dwarf  walls  radiating  from  the  centre,  varying  from  6 inches  to 
15  inches  apart,  and  carried  to  a uniform  height  of  7 inches 
above  the  level  of  the  floor  at  its  circumference ; expanded  metal 
is  laid  on  these  walls  over  the  whole  area,  and  on  this  the  filter- 
ing material  is  placed ; this  method  of  construction  gives  a clear 
space  of  7 inches  between  the  filtering  material  and  the  filtrate 
lying  on  the  concave  floor. 

The  filter  is  surrounded  by  a channel  which  collects  the  filtrate 
and  conducts  it  to  the  outlet  on  the  outer  rim  of  the  floor,  a 
9-inch  pigeon-hole  wall  of  blue  Staffordshire  bricks  is  built  in 
cement,  and  carried  up  to  a height  of  7 feet  6 inches  above  the 
expanded  metal  floor.  This  filter  is  filled  with  four  different 
classes  of  material,  viz. : clinker,  hard  broken  bricks,  honeycomb 
slag,  and  gas  coke.  These  were  filled  in  separately  and  form 
four  distinct  vertical  sections  in  the  filter,  the  cubic  contents  of 
each  section  of  the  filter  is  as  follows : 1492  cubic  yards  clinker, 
312  cubic  yards  hard  broken  bricks,  189  cubic  yards  honeycomb 
slab,  and  189  cubic  yards  gas  coke. 

This  arrangement  was  adopted  with  the  view  of  ascertaining 
the  value  of  each  material  as  a filtering  medium,  both  as  to  its 
suitability  as  a habitat  for  nitrifying  bacteria  and  also  as  to  its 
lasting  properties. 

It  is  perhaps  rather  early  yet  to  state  definitely  which 


SEWERAGE  AND  SEWAGE  DISPOSAL,  YORK. 


19 


material  will  ultimately  prove  most  efficient  in  these  respects, 
but  for  the  general  information  the  Author  appends  the  results 
obtained  up  to  date. 

This  filter  (No.  2)  was  started  on  April  29,  1903,  and  up  to 
February  23,  had  passed  on  the  average  362  gallons  per  square 
yard  per  twenty-four  hours,  or  1,752,000  gallons  per  acre  per  day. 

With  this  quantity  the  following  results  were  obtained. 

Analyses  of  effluents  from  No.  2 filter  showing  results  from 
different  filtering  media.  Average  of  five  analyses  in  grains  per 
gallon. 


— 

Sewage. 

Broken 

Bricks. 

Honeycomb 

Slag. 

Coke. 

Clinker. 

Oxygen  absorbed  4 j 
hours  at  80°  . \ 

5-80 

0*697 

88  p.c. 

0*668 
88-5  p.c. 

0-497 
91*6  p.c. 

0*481 
91-7  p.c. 

Albuminoid  am-f 

monia  . . . \ 

1-18 

0*122 

89  *6  p.c. 

0-103 
90-4  p.c. 

0-078 
93*4  p.c. 

0*084 
92-8  p.c. 

Calcium  nitrate 

Nil 

7*53 

7*69 

9-43 

9*00 

In  comparing  the  results  obtained,  it  should  be  borne  in 
mind  that  this  is  a comparatively  new  filter,  that  had  only  been 
working  for  a few  months. 

In  addition  to  the  samples  taken  from  the  various  filtering 
media  other  samples  of  the  combined  flow  from  all  four  materials 
were  taken  on  eight  occasions  between  September  15,  1903,  and 
March  22, 1904 ; the  following  is  the  average  in  grains  per  gallon : 


— 

Oxygen 

Absorbed. 

Albuminoid 

Ammonia. 

Calcium  Nitrate. 

Sewage  . . 

5*74 

1*24 

.. 

Effluent 

0*54 

0*096 

7-945 

The  average  flow  per  square  yard  per  twenty-four  hours 
during  this  period  has  been  398  gallons. 

Another  point  of  considerable  importance  is  the  durability 
of  the  various  materials  under  the  conditions  that  obtain  in  the 
filter.  This  is  not  a subject  on  which  it  is  possible  to  get  very 
reliable  information  over  a short  period,  i.e.  November  20, 1903, 
to  March  30,  1904.  The  Author  has  however,  ascertained  that 


20  SEWERAGE  AND  SEWAGE  DISPOSAL,  YORK. 

fine  grit  has  come  away  from  the  different  sections  in  the 
following  proportions  : 

Without  going  into  details,  it  can  only  be  said  at  present 
that  during  the  period  the  filter  (No.  2)  was  under  observation 
for  this  purpose,  i.e.  from  November  1903  to  March  1904,  there 
does  not  appear  to  have  been  any  degradation  of  the  filtering 
materials,  or  if  there  has  been,  the  filter  has  retained  the  result 
of  the  breaking  down  of  the  material ; on  the  other  hand,  of  the 
total  quantity  of  mineral  matter  carried  on  to  the  filter  by  the 
tank  effluent,  certain  portions  have  been  retained : the  broken 
bricks  retained  61  per  cent.,  the  slag  61  per  cent.,  the  coke 
47  per  cent.,  and  the  clinker  62  per  cent. 

There  are  a great  many  points  in  connection  with  the  bacterial 
system  of  sewage  purification  on  which  it  is  desirable  that  we 
should  have  definite  and  reliable  information,  so  that  in  design- 
ing a scheme  the  different  parts  should  be  so  proportioned  that 
the  best  results  may  be  obtained  at  the  least  possible  outlay.  It 
has  occurred  to  the  writer  and  doubtless  to  most  of  those  present 
that  the  most  efficient  length  for  a septic  tank  is  a factor  that  it 
would  be  desirable  to  have  definitely  settled  ; there  are,  however 
so  many  conditions  to  consider  that  it  is  only  by  contributions 
to  a common  stock  of  knowledge  that  we  can  hope  to  arrive  at  a 
safe  conclusion. 

As  a small  contribution  on  the  subject  the  following  infor- 
mation may  be  useful. 

Two  tanks,  each  164  feet  long  by  40  feet  wide  have  been 
used  as  open  septic  tanks,  the  flow  from  the  first  passing  through 
the  second  ; the  velocity  of  the  flow  for  some  days  before  and 
after  the  observations  to  be  referred  to  was  0*28  feet  per  minute, 
or  16f  feet  per  hour,  and  the  quantity  passing,  628,000  gallons 
per  twenty-four  hours. 

Samples  of  the  flow  were  taken  at  the  inlet  (raw  sewage)  and 
at  various  distances  between  the  inlet  and  the  outlet,  whence  it 
passed  to  the  continuous  filters.  The  results  are  given  in  the 
tcble  on  page  21.  _ 

It  would  appear  with  a sewage  of  the  composition  given,  with 
a velocity  of  0*28  feet  per  minute,  that  no  adequate  progress  in 
purification  was  effected  after  flowing  through  the  tank  for  a 
distance  of  225  feet ; the  items  of  oxygen  absorbed  and  albu- 
minoid ammonia  remaining  stationary  during  the  further  flow  of 
100  feet.  It  will  be  observed  that  there  was  a continued  reduc- 


SEWERAGE  AND  SEWAGE  DISPOSAL,  YQRK. 


21 


Analysis  of  Septic  Tank  Contents  taken  on  March  15,  1904. 
Grains  per  gallon . 


Distance 
from  Sewage 
Inlet. 

Free 

Ammonia. 

Albuminoid 

Ammonia. 

Oxygen 

Absorbed. 

Total 

Suspended 

Solids. 

Mineral 

Suspended 

Solids. 

Organic 

Suspended 

Solids. 

feet. 

0 

2 555 

0-665 

3160 

34-3 

8-4 

25-9 

18 

1-435 

0-595 

2-673 

30-1 

8-4 

21  *7 

72 

1-400 

0-560 

2-43 

28-0 

7-7 

20-3 

102 

1-085 

0-420 

2-43 

25-9 

70 

18-9 

132 

1-260 

0-420 

2-31 

22-4 

6-3 

161 

195 

1-575 

0-385 

1-944 

21-0 

4-9 

161 

225 

1-575 

0-315 

1-6 

20-3 

4-9 

15-4 

255 

1-260 

0-315 

1-6 

17*5 

4-9 

12-6 

308 

M90 

0-315 

1-6 

14-7 

3-85 

10-85 

326 

1-190 

0-315 

1-6 

14-35 

3-85 

10-5 

tion  in  the  free  ammonia  and  solids,  both  mineral  and  organic, 
but  this  reduction  would  not  be  sufficient  to  warrant  the  con- 
struction of  a longer  tank.  (See  Table  above.) 

It  is  evident  that  this  tank  does  something  more  than  liquefy 
the  organic  solids,  as  the  sewage  on  this  occasion  was  purified 
during  its  progress  through  the  tank  to  the  extent  of  about  50 
per  cent,  both  in  oxygen  absorbed  and  albuminoid,  and  it  is 
evident  that  this  improvement  is  not  confined  to  the  later  period 
of  its  flow  through  the  tank.  As  the  percentage  of  purification  is 
greatest  in  the  first  18  feet  of  flow,  gradually  diminishing  as  it 
proceeds  until  it  reaches  a point  when  a further  flow  of  100  feet 
fails  to  effect  any  further  improvement  in  the  sewage,  the  in- 
ference is  that  both  anaerobic  and  aerobic  bacteria  are  working 
throughout  the  whole  effective  length  of  the  tank,  and  that  when 
a certain  stage  of  purification  has  been  reached  a different  pro- 
cess is  required  to  carry  on  the  work.  The  difference  in  the 
extent  and  rapidity  of  the  purifying  process  is  very  marked 
when  passing  through  the  filter.  In  the  last  100  feet  of 
flow  through  the  tank  the  sewage  has  evidently  remained  in 
a comparatively  stable  condition ; no  purification  took  place, 
whereas  in  the  fifteen  minutes  taken  to  pass  through  a depth 
of  6 feet  9 inches  of  filter,  the  purification  increased  to  72  per 


22 


SEWERAGE  AND  SEWAGE  DISPOSAL,  YORK. 


cent.,  bringing  up  the  total  purification  by  tank  and  filter  to 
86  per  cent. 

The  strength  of  the  sewage  on  this  occasion  was  very  much 
below  what  usually  obtained.  The  average  strength  of  the 
sewage  during  the  past  six  months  has  been  6*44  grains  per 
gallon  oxygen  absorbed. 

The  action  on  the  suspended  solids  is  very  interesting ; of 
the  total  quantity  entering  the  tank  with  the  sewage  75  per 
cent,  was  organic  and  25  per  cent,  mineral.  On  leaving  the 
tank  the  suspended  solids  had  been  reduced  to  58  per  cent.,  and 
this  was  composed  of  73  per  cent,  of  organic  suspended  matter, 
and  27  per  cent,  mineral,  this  approximates  very  closely  to  the 
proportions  in  the  raw  sewage.  (See  Table,  p.  21.) 

Similar  observations  taken  over  ten  hours  on  October  6, 1903, 
when  the  sewage  showed  9 • 73  grains  per  gallon  oxygen  absorbed, 
tend  generally  to  confirm  the  results  above  described  so  far  as 
the  purification  is  concerned.  The  velocity  was  0*105  feet  per 
minute,  or  6 * 3 feet  per  hour,  and  the  quantity  passing  through, 
238,000  gallons  per  24  hours.  As  in  the  former  case,  there 
was  no  reduction  in  oxygen  absorbed  during  the  last  100  feet  of 
flow. 

With  this  velocity  92  per  cent,  of  total  suspended  solids 
were  deposited  in  the  first  18  feet,  i.e.  in  the  grit  chamber,  while 
in  the  former  case  with  a velocity  of  0*28  feet  per  minute  only 
58  per  cent,  of  the  suspended  solids  were  so  deposited.  The 
suspended  solids  in  the  sewage  on  this  occasion  comprised  52 
per  cent,  organic  and  48  per  cent,  mineral.  The  total  solids 
were  reduced  during  the  flow  through  the  tank  to  8 per  cent., 
and  this  was  composed  of  75  per  cent,  organic  and  25  per  cent, 
mineral,  so  that  notwithstanding  that  the  sewage  in  the  latter 
case  contained  nearly  three  times  the  quantity  of  suspended  solids 
and  a velocity  through  the  tank  of  only  6 * 3 feet  per  hour,  as 
against  16|  feet  in  the  former  case.  The  proportionate  results  on 
leaving  the  filter  were  practically  identical. 


Temperatures. 

A large  number  of  observations  have  been  taken  of  the 
temperature  of  the  sewage,  filter  bed,  filtrate  and  atmosphere 
during  the  past  three  years.  Shortly  the  results  are  as  follows : 


SEWERAGE  AND  SEWAGE  DISPOSAL,  YORK. 


23 


In  the  winter  the  sewage  averaged  8 degrees  above  the  atmosphere, 
the  filtrate  3 degrees  below  the  sewage.  The  filter  itself  averaged 
from  2 degrees  below  the  sewage  to  1 degree  above,  the  lower 
temperature  being  in  that  part  of  the  filter  nearest  to  the  outside 
wall. 


Aeration. 

There  can  be  little  doubt  that  this  form  of  filter  wholly  above 
ground  lends  itself  admirably  to  thorough  aeration.  Observations 
have  been  taken  at  the  openings  in  the  pigeon-hole  wall  at  the 
termination  of  the  perforated  pipes  by  means  of  an  anemometer  ; 
the  results  show  that  notwithstanding  the  numerous  openings  for 
the  admission  of  air  into  the  filter  the  velocity  on  the  windward 
side  varied  from  350  to  1050  feet  per  minute,  while  on  the  lee 
side  it  varied  from  550  to  1240  feet  per  minute  from  the  filter, 
sufficient  to  satisfy  the  most  voracious  microbe. 

Fish  Life. 

There  is  on  the  table  a photo  of  a fifty  minutes’  catch  of 
roach  and  dace  at  the  outlet  from  the  continuous  filters,  the  few 
fishermen  who  try  their  luck  at  this  place  rarely  have  reason  to 
complain  of  a poor  catch. 


Explanation  of  Diagrams. 

No.  1 Diagram  represents  the  quantities  in  grains  per  gallon 
of  oxygen  absorbed  in  four  hours  at  80°  F.  by  sewage  and  No.  1 
filter  effluent  between  July  1900  and  March  1904,  also  the 
number  of  gallons  put  on  to  the  filter  per  square  yard  per 
twenty-four  hours  during  the  same  period.  The  sewage  is 
shown  by  a full  line,  the  effluent  by  a dotted  line,  and  the 
volume  per  square  yard  by  a dot  and  dash  line. 

The  figures  on  the  left  hand  side  of  the  diagram  represent 
grains  in  their  reference  to  the  sewage  and  effluent,  and  hun- 
dreds of  gallons  in  their  reference  to  the  quantities  put  on  to 
the  filter. 

No.  2 Diagram  show6  the  depth  of  sludge  in  the  open  septic 
tank  after  one  year's  use  by  a dotted  line,  and  the  depth  of  sludge 
alter  two  years'  use,  when  an  additional  tank  had  been  added, 


24 


SEWERAGE  AND  SEWAGE  DISPOSAL,  YORK. 


by  a full  line.  The  horizontal  lines  represent  depths  in  inches, 
and  the  vertical  lines  length  in  feet  from  the  sewage  inlet. 

No.  3 Diagram  represents  by  vertical  lines  the  average  depth 
of  sludge  in  inches  over  the  whole  area  of  the  tanks  at  the  dates 
given  at  bottom  of  diagram.  The  tanks  have  been  in  use  from 
May  7,  1902.  The  diagram,  it  will  be  seen,  commences  on 
January  21,  1903,  so  that  the  7 inches  shown  on  the  latter  date 
represents  the  accumulated  deposit  of  sludge  over  the  whole 
area  between  those  two  dates. 


DISCUSSION. 

Mr.  J.  T.  Eayrs  : I quite  agree  with  the  Author  of  the  paper 
when  he  says  you  cannot  fix  any  arbitrary  standard  for  sewage 
effluent.  It  is  a point  which  some  people,  and  some  county 
councils  insist  on,  but  it  is  very  obvious  that  it  is  quite  a fallacy 
to  insist  upon  a certain  percentage  of  purification  when  one  does 
not  know  the  strength  and  quality  of  the  sewage  one  is  dealing 
with.  In  smaller  towns  the  sewage  may  not  be  one-fifth  of  the 
strength  of  the  sewage  in  larger  places  having  trades  waste  to 
deal  with,  and  when  you  speak  of  90  per  cent,  of  purification, 
the  effluent  may  really  be  worse  than  the  crude  sewage  of  a 
smaller  town.  That  shows  the  fallacy  of  taking  a percentage 
of  purification  as  the  basis.  I am  very  glad  Mr.  Creer  has 
referred  to  the  question  of  fish  caught  at  the  sewage  outfall, 
because  I think  it  was  on  my  suggestion  when  here  some  time 
ago  that  the  practice  was  adopted  of  having  the  fish  weighed 
when  taken.  I was  very  much  struck  when  at  the  works  by 
seeing  anglers  fishing  nowhere  along  the  river  but  at  the 
sewage  outfall.  I then  suggested  to  Mr.  Creer  that  he  should 
keep  a record  of  the  names  of  the  fishermen  and  the  quantities 
of  fish  taken,  because  the  information  might  be  useful  in  any 
ulterior  proceedings  by  the  County  Council  or  the  River  Board. 
These  records  come  in  very  handy  when  required.  I would 
suggest  if  the  diagrams  shown  on  the  walls  are  published  in  our 
Proceedings,  that  a few  more  explanatory  notes  will  add  to  their 
value.  The  quality  of  the  river  water  above  the  intake  appears 
to  be  practically  the  same  as  the  quality  at  the  sewage  outfall, 
where  the  effluent  is  discharged  into  it,  and  after  the  river  has 
passed  through  the  entire  city.  That  indicates  to  me  two  things  : 


DISCUSSION. 


25 


one  that  there  is  very  little  if  any  pollution  going  on  as  the  river 
passes  through  the  city— a great  deal,  if  not  all  the  sewage  has 
been  diverted  from  the  river  and  turned  into  the  sewers — and 
the  second  point  shows  that  the  effluent,  although  not  quite  so 
good  as  the  river  water,  still  after  it  enters  the  river  there  is  no 
appreciable  effect  on  the  quality.  As  to  experiments  4 and  5, 
No.  4 is  an  experiment  which  has  been  carried  out  now  on  a 
larger  scale — open  septic  tanks  and  continuous  filtration ; No.  5 
is  open  septic  tank  effluent  and  double  contact.  Although  the 
depth  of  filtration  with  the  double  contact  is  exactly  the  same 
as  with  continuous  filtration,  it  only  passed  about  one-twelfth 
of  the  quantity  per  square  yard,  or  gallons,  per  acre,  and  the 
effluent  was  not  nearly  so  good.  That  is  very  conclusive  as 
regards  the  sewage  of  York.  Whether  it  applies  to  other  places 
I am  not  prepared  to  say,  but  so  far  as  York  is  concerned  it 
shows  the  great  superiority  of  continuous  filtration  over  the 
double  contact  system. 

Mr.  A.  M.  Fowler  : Municipal  engineers  know  that  in  towns 
of  a similar  character  to  York  where  they  have  few  manufactories, 
large  sums  of  money  are  now  being  spent  in  schemes  of  this 
character.  But  to  apply  this  system  so  admirably  worked  as 
in  York  to  other  towns  it  is  desirable  to  have  all  the  facts  bear- 
ing upon  it,  the  number  of  manufactories  and  the  quantity  of 
manufacturing  refuse.  In  Leeds,  Manchester  and  towns  of  that 
class,  the  manufacturing  refuse  turned  into  the  sewers  creates  an 
enormous  difficulty  in  the  purification  of  the  sewage,  whereas  at 
Exeter  and  other  places  similar  to  York,  there  is  practically  no 
difficulty  whatever,  and  you  can  get  a splendid  effluent.  There- 
fore, if  we  could  get  statistics  bearing  upon  this — giving  the 
number  of  water-closets,  privies,  ashpits,  the  number  of  manu- 
factories, the  quantity  of  trade  effluents  and  the  trades  carried 
on — it  would  be  very  useful  to  us.  As  to  fish  living  at  the 
outfall  of  a sewage  effluent,  Prussian  carp  will  live  in  almost 
any  water.  In  1872  when  I designed  the  works  at  Leeds,  where 
we  had  the  A.  B.  C.  process  in  operation,  I had  fish  living  there 
in  globes  for  five  months,  some  in  the  town’s  water  and  others 
in  the  effluent  water  from  the  sewage  tanks ; one  died  in  the 
town’s  water  three  days  before  the  fish  in  the  sewage  effluent. 
So  you  can  get  an  effluent  sufficiently  good  for  fish  to  live  in, 
but  in  doing  so  you  are  going  to  a very  great  expense. 

Mr.  J.  P.  Spencer:  Mr.  Creer  has  placed  before  us  the 


26 


SEWERAGE  AND  SEWAGE  DISPOSAL,  YORK. 


development  and  change  from  one  system  to  another,  and  I 
think  he  has  made  it  demonstrable  that  for  a city  like  York  the 
open  septic  tank  with  continuous  filtration  is  the  best.  I knew 
York  long  ago,  and  I have  been  in  it  in  more  recent  times,  and 
it  seems  to  me,  judging  from  the  two  periods,  that  the  river  is 
in  a much  better  state  now  than  formerly,  notwithstanding  the 
greater  volume  of  sewage  effluent  put  into  it. 

Mr.  A.  D.  Greatorex  : I should  like  to  propose  a very  hearty 
vote  of  thanks  to  Mr.  Creer  for  his  valuable  paper.  As  regards 
Mr.  Creeps  statement  as  to  the  proportion  the  volume  of 
effluent  bears  to  the  volume  of  the  stream  into  which  the 
effluent  discharges,  that  is  a very  important  point.  In  my  own 
case  the  volume  of  the  effluent  is  one-thirtieth  of  the  stream 
into  which  it  discharges,  and  from  analysis  the  river  is  really 
worse  than  the  crude  sewage  of  the  town,  owing  to  the  sewage 
discharge  higher  up  the  stream.  To  make  a standard  for  a place 
like  this  would  be  grossly  unfair. 

Dr.  Wilson,  Chief  Inspector  of  the  West  Eiding  Eivers 
Board : I am  really  glad  of  the  opportunity  of  thanking  Mr.  Creer 
for  giving  me  the  chance  to  be  present  to  hear  his  interesting 
paper.  There  are  several  points  in  the  paper  I should  like  to  refer 
to.  First  as  to  standard  of  purification.  I quite  agree  with 
Mr.  Creer  that  an  arbitrary  chemical  standard  is  not  one  to  be 
advocated.  Several  times — very  frequently  indeed — the  Eivers 
Board  have  been  asked  to  fix  a chemical  standard  ; it  would,  as 
you  can  easily  see,  make  easier  the  work  of  the  Board ; but  they 
have  no  legal  power  to  do  so.  It  would  be  absurd  to  fix  the 
same  standard  for  an  effluent  which  discharges  into  a navigable 
river  like  the  Ouse  and  an  effluent  which  discharges  into  a 
small  stream  which  is  afterwards  used  for  drinking  purposes. 
Mr.  Creer  has  pointed  out  the  fallacy  of  adopting  a percentage 
of  purification  as  a standard.  The  sewage  in  the  West  Eiding 
differs  enormously,  and  a purification  of  90  per  cent,  at  York 
would  produce  an  effluent  much  better  than,  say,  at  Bradford, 
which  has  one  of  the  worst  sewages  in  the  Eiding. 

Mr.  Creer  has  mentioned  the  pressure  exercised  by  the 
Eivers  Board  and  the  complaints  of  the  Eivers  Board  as  to  the 
state  of  the  Ouse.  He  rather  gives  himself  away  in  a previous 
paragraph,  when  he  says  the  effect  is  perceptible  half  a mile 
below  the  outlet  from  the  sewage  works,  and  that  on  many 
occasions  the  chemical  analysis  of  the  water  was  worse  below 


DISCUSSION. 


27 


than  it  was  above  the  outfall.  Mr.  Creer  does  not  state  the  real 
ground  of  the  complaint  of  the  Rivers  Board,  and  this  I mention 
to  show  the  difference  between  a bacterial  effluent  and  a chemical 
effluent.  In  1901,  a warm  and  dry  year,  the  whole  of  the  weir 
on  the  river  below  the  sewage  works  was  covered  with  sewage 
fungus,  and  the  death  of  large  numbers  of  fish  was  due  to  this 
sewage  fungus.  That  was  the  effect  of  a chemical  effluent  dis- 
charged without  filtration  into  the  river.  An  effluent,  such  as 
that  Mr.  Creer  is  now  producing  from  the  sprinkling  filters,  has 
just  the  opposite  effect.  The  effluent  is  in  such  a condition  that 
it  improves  after  being  discharged  into  the  river,  instead  of,  like 
a chemical  effluent,  undergoing  reaction  and  deterioration. 

There  are  one  or  two  points  on  which  I would  like  to  warn 
some  of  the  members  present  as  to  the  making  of  loose  deduc- 
tions from  the  results  obtained  by  Mr.  Creer.  The  strength  of 
the  sewage  is  given  in  the  paper.  The  amount  of  sewage  per  head 
of  the  population  shows  that  a good  deal  of  subsoil  water  is  mixed 
with  the  sewage  of  York,  and  the  results  of  analysis  show  it  is  a 
weak  sewage.  There  are  sewages  in  Yorkshire  which  give  twelve 
times  the  oxygen  absorbed  of  that  of  York,  and  the  engineers 
must  not  expect  the  same  results  with  such  sewages  as  Mr.  Creer 
is  able  to  obtain  at  York.  Then  mention  is  made  in  the  paper  of 
the  suspended  matter  in  the  filter  effluent.  In  the  case  of  the 
filters  at  Leeds  and  many  other  places  throughout  the  West 
Riding,  the  amount  of  suspended  matter  is  a drawback  to  these 
percolating  filters,  and  the  effluents  require  after-treatment  for 
its  removal.  It  accounts  for  about  50  per  cent,  of  the  impurity 
of  the  effluents.  It  is  not  an  offensive  matter — in  fact,  it  is  much 
like  garden  mould  in  appearance,  but  still  it  is  an  impurity 
which  should  be  removed  before  discharge  into  a stream.  Again, 
later  on  in  the  paper,  where  Mr.  Creer  gives  a table  of  analyses 
of  the  effluents  from  different  materials  which  he  is  using,  I 
think  it  should  be  mentioned  that  the  sizes  of  the  materials 
used  are  very  different,  and  to  my  mind  the  difference  in  results 
between  clinker  and  broken  bricks  is  due  more  to  the  sizes  of 
the  materials  than  to  their  nature. 

This  question  of  bacterial  purification  is  now  quite  out  of 
the  hands  of  the  chemists  and  the  biologists,  and  wholly  in  the 
hands  of  you  engineers,  and  I am  glad  to  know  that  so  many 
able  men  are  working  at  the  details  of  these  methods  of  the 
bacterial  purification  of  sewage.  We  have  not  yet,  however, 


28 


SEWERAGE  AND  SEWAGE  DISPOSAL,  YORK. 


quite  got  rid  of  chemical  methods.  There  are  many  places 
where  trade  refuse  is  mixed  with  domestic  sewage  where 
chemicals  are  still  used  with  advantage. 

Mr.  C.  F.  Wike  : Unfortunately  I have  not  had  time  to  go 
thoroughly  into  the  statistics  contained  in  Mr.  Creeps  valuable 
paper,  which  embodies  the  results  of  great  thought  and  experi- 
ence in  connection  with  the  sewage  question.  Mr.  Creer’s 
conclusions  are  not  theories  only,  and  whether  they  are  right  or 
wrong  we  know  they  have  been  carefully  and  honestly  thought 
out.  With  respect  to  the  standard  of  purity  required  by  the 
Eivers  Board  and  its  application  to  rivers  of  different  volume — 
it  does  seem  reasonable  that  some  distinction  should  be  made 
between  tidal  rivers  and  those  which  are  canalised,  where  in 
times  of  drought  the  effluent  from  a sewage  works  may  be  the 
only  feeder.  Naturally,  in  the  latter  case,  the  effluent  should 
be  a very  good  one.  I thoroughly  agree  with  Mr.  Creeps  para- 
graph as  to  the  position  of  towns  which,  during  the  last  fifteen 
or  twenty  years,  have  honestly  tried  to  purify  their  sewage,  and 
have  spent  large  sums  of  money  in  this  way.  In  Sheffield  we 
some  time  ago  spent  150,000Z.  to  200,000Z.  on  the  works  and 
outfall  sewers,  and  now  the  Local  Government  Board  and  the 
Eivers  Board  tell  us  it  is  necessary  to  begin  all  over  again,  so 
far  as  the  works  are  concerned.  Seeing  that  we  have  a Sewage 
Commission  sitting,  whose  final  report  may  shortly  be  expected, 
we  have  not  thought  it  unreasonable  to  hasten  slowly,  but  the 
Eivers  Board  are  of  different  opinion,  and  consequently  it  has 
been  necessary  to  prepare  a scheme  which  will  involve  an  ex- 
penditure of  possibly  300, 000£.  to  400, 000£.,  and  this  is  now 
under  the  consideration  of  the  Local  Government  Board.  It  is 
shown  by  Mr.  Creeps  summaries  that  he  has  got  very  satisfac- 
tory results  by  treating  the  sewage  in  an  open  septic  tank  and 
passing  the  effluent  through  a continuous  filter,  but  of  course, 
as  has  already  been  stated,  there  is  a difference  between  the 
sewage  of  various  towns.  In  Sheffield,  after  very  careful  analysis, 
we  have  come  to  the  conclusion  that  the  best  effluent  is  obtained 
by  passing  the  crude  sewage  through  a settling  tank,  and  after- 
wards through  the  double  contact  beds.  We  take  samples  every 
hour  which  are  mixed  at  the  end  of  the  day,  so  that  we  get  a 
correct  average,  and  these  are  then  analysed.  We  get  a purifica- 
tion of  from  95  to  97  per  cent,  by  this  means,  and  it  is  upon 
this  basis  that  we  are  proposing  to  extend  our  works. 


DISCUSSION. 


29 


Mr.  E.  P.  Hirst:  I should  like  to  add  my  thanks  to  Mr. 
Creer  for  the  very  valuable  paper  which  has  been  placed  in  our 
hands.  The  time  appears  to  be  arriving  when  with  other  seaside 
towns  we  at  Southport  may  have  to  clarify,  if  not  purify,  our 
sewage.  I notice  that  Mr.  Creer  states  that  1,730,000,000 
gallons  were  lifted  per  annum.  Now  that,  with  a population  of 
80,000,  gives  about  60  gallons  per  head  per  day.  I should  like 
to  know  how  much  Mr.  Creer  considers  sewage  proper,  and 
how  much  subsoil  water.  Then  again,  speaking  of  albuminoid 
ammonia,  he  gives  it  in  parts  per  100,000.  I should  like  to 
know  if  the  percentages  of  oxygen  absorbed  are  given  in  grains 
per  gallon,  or  whether  they  are  also  given  in  parts  per  100,000. 
It  would  materially  help  us  to  know  how  the  strength  of  the 
York  sewage  compares  with  that  of  our  own  localities.  Mr. 
Creer  states  in  experiment  No.  1 that  the  gallons  per  square 
yard  treated  were  42*89.  This  I take  it  was  in  the  three 
fillings  of  the  bed.  Now,  as  the  capacity  of  the  bed  appears  to 
be  something  like  60,000  gallons,  or  rather,  let  me  put  it  in 
another  way,  as  a cubic  yard  would  contain  about  168  gallons, 
and  Mr.  Creer  only  put  on  14  gallons  per  square  yard  per 
filling,  is  only  about  one-twelfth  of  the  total  capacity  of  the 
bed,  and  inasmuch  as  the  filtering  medium  would  probably  not 
take  up  more  than  two-fifths  or  one-third  of  the  total  capacity 
of  the  bed,  I cannot  quite  understand  the  small  quantity  which 
appears  to  be  treated.  Either  the  beds  could  not  have  been 
filled,  or  there  must  have  been  a considerable  silting  up  in 
them.  In  regard  to  experiment  No.  4,  I do  not  know,  but  I 
presume  that  the  septic  tank  that  was  used  in  this  experiment 
was  the  same  as  the  one  which  was  used  in  experiment  No.  5. 
I merely  want  to  be  quite  sure  that  I understand  that  aright, 
and  if  so,  I should  like  to  know  (as  I see  there  are  two  tanks), 
whether  the  sewage  is  allowed  to  stand  in  one  of  these  septic 
tanks,  or  whether  there  is  a continuous  flow  through  it.  I 
should  be  glad  also  to  know  the  cost  of  the  circular  filters,  and 
the  sizes  of  the  materials  used  in  their  construction. 

Alderman  Sir  Joseph  Sykes  Kymer:  In  former  times  we 
had  a very  easy  system  of  disposal.  We  just  turned  the  sewage 
into  the  river.  We  stuck  to  that  system  as  long  as  we  could, 
because  we  knew  when  we  departed  from  it  that  it  would  be  a very 
expensive  process.  We  only  departed  from  it  under  pressure. 

Mr.  J.  Lobley  : I beg  to  second  the  vote  of  thanks.  In  some 


30 


SEWERAGE  AND  SEWAGE  DISPOSAL,  YORK. 


respects  there  is  the  most  remarkable  contrast  between  my  own 
town  and  York,  but  there  is  one  similarity  in  the  enormous 
amount  of  water  to  be  dealt  with  at  the  sewage  disposal  works. 
I gather  from  Mr.  Creer’s  paper  that  he  has  to  deal  with  the 
very  large  volume  of  sewage  of  60  gallons  per  head  per  day. 
In  my  case  I have  had  a good  deal  of  mine  water  coming  into 
the  sewers,  and  the  Local  Government  Board  insist  upon  multi- 
plying that  mine  water  by  six.  In  order  to  provide  bacteria 
beds  for  that  means  an  enormous  expense. 

The  vote  of  thanks  having  been  unanimously  passed, 

Mr.  A.  Creer,  in  reply,  said : I must  express  my  hearty 
thanks  for  the  reception  you  have  given  to  my  paper,  and  the 
interesting  discussion  that  has  followed  the  perusal  of  it.  I 
dare  say  some  of  you  will  feel  with  me  that  this  question  of 
sewage  disposal  is  a most  fascinating  one,  and  if  once  you  begin 
to  take  an  interest  in  the  subject,  it  seems  to  absorb  all  one’s 
spare  time.  I think  it  quite  likely  that  if  the  works  had  been 
seen  before  the  paper  was  discussed,  there  would  have  been  no 
necessity  to  ask  some  of  the  questions.  I do  not  propose  to 
answer  all  the  questions  now.  If  it  is  found  that  there  is  not  time 
for  further  discussion  after  visiting  the  works  I shall  be  pleased 
to  answer  any  questions  sent  to  me  in  writing,  so  that  the  replies 
may  appear  in  the  Proceedings.  Dr.  Wilson  made  some  remarks 
as  to  the  filtering  media.  It  is  quite  likely  that  the  difference 
in  grade  of  the  material  may  have  had  something  to  do  with 
the  results  obtained.  But,  of  course,  you  cannot  get  definite 
results  from  one  experiment.  It  is  quite  possible  that  in  the 
further  extension  of  the  filtering  provision  we  may  try  different 
materials  and  different  sizes.  The  curious  thing  is,  that  the 
clinker  is  very  much  smaller  than  the  other  three  materials ; 
the  coke  is  as  large  or  larger  than  the  broken  brick,  but  is  not 
larger  than  the  honeycomb  slag.  The  slag  is  a very  tough  ma- 
terial and  difficult  to  break.  You  will  see  that  the  coke  which 
is  as  large  as  the  slag,  and  larger  than  the  other  materials,  gives 
us  the  best  results.  That  gives  you  an  idea  of  the  value  of 
coke  as  a filtering  material  as  apart  from  size.  I would  like  to 
say,  in  regard  to  Mr.  Hirst's  question  as  to  the  analyses,  that 
the  earlier  analyses  referred  to  were  taken  very  early  on  in  the 
history  of  sewage  disposal  at  York.  They  were  made  by  a 
Leeds  chemist,  and  he  gave  us  the  results  in  parts  per  100,000. 
All  the  other  results  are  in  grains  per  gallon.  The  volume  of 
sewage  to  quantity  of  water  pumped  into  the  city  averages 


DISCUSSION. 


31 


35  gallons  per  head  per  day.  The  quantity  pumped  by  the 
Corporation  at  the  pumping  station  is  about  41  gallons  per 
head  per  day.  We  have  many  sewers  that  are  below  the  level 
of  the  two  rivers — the  Ouse  and  the  Foss — and  some  of  them 
are  very  old,  practically  centuries  old,  and  you  will  understand 
the  difficulty  of  tracing  these  out  and  cutting  them  off  from 
the  intercepting  sewers  which  take  the  sewage  down  to  the 
works.  I hope  the  Local  Government  Board  and  the  Rivers 
Board  will  give  consideration  to  the  fact  that  the  water  we 
treat  is  practically  double  what  we  ought  to  legitimately  treat 
in  the  city  of  York. 

A cordial  vote  of  thanks  to  the  Lord  Mayor  and  Corporation 
for  the  use  of  the  Council  Chamber  for  the  meeting  was  passed 
unanimously. 

Communicated  Discussion. 

Mr.  E.  J.  Silcock  : I wish  to  direct  special  attention  to  the 
comparative  results  obtained  in  the  new  continuous  filter  with 
the  different  materials  used  as  the  filtering  medium.  These 
results  are  set  out  in  the  table  given.  It  has  long  been  my 
opinion  that  the  materials  which  were  utilised  in  nearly  all  the 
earlier  experiments,  i.  e.  coke  and  clinkers,  are  of  much  too  soft  a 
nature  to  be  used  as  part  of  a permanent  works,  especially  where 
these  works  are  being  carried  out  by  money  for  which  loans 
have  been  obtained,  and  I have  strongly  urged  the  desirability  of 
using  harder  materials,  such  as  slag,  lava,  granite,  etc.  Holding 
these  views,  it  is  disappointing  to  find  that  the  results  of 
Mr.  Creer’s  experiments  extending  over  a considerable  period 
show  that  the  degree  of  purification  obtained  by  using  broken 
bricks  and  slag,  although  satisfactory  in  themselves,  are  yet 
sensibly  inferior  to  those  obtained  by  using  coke  and  clinkers. 
Before  finally  accepting  these  results  I should  be  glad  if  the 
Author  would  give  full  particulars  as  to  the  size  to  which  the 
various  materials  were  graded,  as  this  point  may  explain  to  some 
extent  the  difference  in  the  results  obtained.  If  the  broken 
bricks  and  slag  are  larger  than  the  coke  and  clinker  they  will 
permit  more  solids  to  be  washed  through  the  bed,  and  this  may 
cause  the  analyses  to  show  the  results  in  favour  of  coke  and 
clinkers.  However  this  may  be  I would  urge  upon  those 
Members  who  have  the  opportunity  of  comparing  results  ob- 
tained by  various  materials  to  take  every  opportunity  of  doing  so 
and  of  putting  on  record  their  experience.  I may  say  that  in 


32  SEWERAGE  AND  SEWAGE  DISPOSAL,  YORK. 

the  Leeds  experiments  this  question  has  been  carefully  gone 
into,  and  it  has  not  been  found  that  there  was  any  variation 
worth  considering  in  the  degree  of  purification  obtained  from 
various  filtering  media,  and  I have  therefore  considered  that 
the  greater  stability  of  the  material  was  the  most  important 
factor  in  selecting  the  material  which  should  be  used. 

Communicated  Reply, 

Mr.  Creer  : In  reference  to  Dr.  Wilson's  remarks  on  the 
quality  of  the  river  water  half-a-mile  below  the  works,  it  will 
be  seen  on  reference  to  the  paper  that  the  river  water  below  the 
works  was  on  the  average  4 • 5 per  cent,  worse  by  the  oxygen 
absorbed  test  than  above,  and  as  this  percentage  was  on  a very 
low  figure,  viz.  0*270  grains  per  gallon,  it  will  be  seen  that  the 
effect  of  the  effluent  from  the  chemically  treated  sewage  was 
trifling. 

The  replies  to  Mr.  Hirst's  questions  are  given  hereunder. 

The  1730  millions  include  storm  water. 

The  normal  daily  flow  is  about  46  gallons  per  head  per  day ; 
of  this  quantity  about  10  gallons  is  due  to  subsoil  water. 

The  question  as  to  capacity  of  bed  I cannot  follow ; each  of 
the  two  beds  had  a cubic  capacity  equal  to  46,426  gallons,  not 
60,000,  and  the  effluent  from  the  first  bed  passed  through  the 
second.  Probably  Mr.  Hirst  has  had  in  his  mind  a single  contact 
system,  whereas  the  experiment  referred  to  double  contact  when 
the  quantity  treated  was  passed  through  two  filters,  thus  doubling 
the  area  required  for  filtration. 

The  septic  tank  used  for  No.  4 experiment  was  the  same  as 
used  for  No.  5 ; but  in  the  former  case  the  whole  flow  was  used 
in  the  experiment,  while  in  the  latter  only  part,  the  balance 
passing  to  other  experimental  plant. 

Full  particulars  are  given  in  the  paper  as  to  the  method  of 
working  the  tanks. 

The  cost  of  the  100  feet  diameter  filter  was  about  1500£. ; it 
is  obvious  that  a number  of  filters  could  be  put  up  at  a very 
much  less  cost  per  unit. 

Dr.  Wilson  asked  a question  on  the  same  lines  as  Mr.  Silcock, 
this  was  answered  at  the  Meeting  and  appears  in  the  Report. 


LONDON:  PRTNTKD  BY  WILLIAM  CLOWES  AND  SONS.  LIMITED, 

GREAT  WINDMILL  STREET,  W.,  AND  DU E E STREET,  STAMFORD  STREET,  8.E. 


DIAGRAM  No.  1 


Oxygen  Absorbed  in  4 Hours  at  80°  Fah.  (Grains  Per  Gallon). 


Gallons  passing  per  Sq . Yard  per  24  Hours. 


CITY  OF  YORK-  SEWAGE  DISPOSAL 


DIAGRAM  No.  2. 


Diagram  shewing  the  depth  of  sludge  in  the  Open  Septic  Tank 
after  one  and  two  years  use. 


DIAGRAM  No  3. 


Diagram  shewing  the  average  depth  of  sludge  in 
Open  Septic  Tank. 


CITY  OF  YORK  SEWAGE  DISPOSAL. 


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Diagram  shewing  the  various  stages  of  fouling  and  purifying  that 
the  water  passes  through  during  its  passage  from  the  Water  Works 
Intake  to  its  return  to  the  River  at  the  Effluent  Sewage  Outlet. 


N0T1V0  U3d  SNIVaO 


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Diagram  shewing  the  purification  effected  in  the  sewage  during  its  flow  through  the 
Open  Septic  Tank,  the  figures  along  the  bottom  of  the  diagram  shewing  the  distances 
from  the  tank  inlet  where  the  various  samples  were  taken  for  analysis. 


Diagram  shewing  the  gradual  deposition  of  suspended  solids  in  Open  Septic  Tank  as 
the  sewage  flows  through  the  whole  length  of  the  Tank. 


Q1T  Y o F YORK  SEWAGE  DISPOSA L . 


